An electrophotographic apparatus (hereinafter referred to as a "primary apparatus"), e.g., a copying machine or a printer using electrophotographic techniques, comprises a photoconductor having an electrically conductive substrate and a photoconductive layer disposed on the conductive substrate. Typically, the photoconductor is mounted on the primary apparatus by a shaft which is rotatable about the axis of rotation of the cylindrical tubular substrate. As the cylindrical tubular substrate rotates continuously about its axis of rotation, an image is formed by charging up the photoconductor surface, exposing the charged photoconductor surface to form a latent image, developing the latent image with a developing agent containing toner, and copying and fixing the toner image on a supporting means such as paper or the like. After the toner image has been copied, the photoconductor surface is cleaned and discharged so that the photoconductor may be used repeatedly.
For mounting the photoconductor rotatably about its axis of rotation on the primary apparatus, and for rotating the mounted photoconductor, a flange for transmitting the rotational driving force (hereinafter referred to as a "driving flange") is inserted and affixed to an end of the cylindrical tubular substrate. The driving flange has a through-hole into which a metallic shaft is inserted coaxially with the cylindrical tubular substrate, and a gear for transmitting the rotational driving force from the primary apparatus to the substrate. Another flange for fixing the axis of rotation (hereinafter referred to as a "fixing flange") is inserted and affixed to the other end of the cylindrical tubular substrate. The fixing flange has a through-hole into which the metallic shaft is inserted. The driving flange also serves as an electrode for grounding the photoconductor. Recently, resin flanges have been used due to their light weight. Typically, the photoconductor is grounded, at the time the resin flange is installed on the photoconductor, by installing a metallic spring which electrically interconnects the substrate and the shaft.
For high-quality copying or printing, it is necessary to rotate the photoconductor very precisely about its axis of rotation, without wobble or eccentricity. It is important for the photoconductor not to yield under pressure during the copying or cleaning process. Thus, the driving flange should be installed tightly on the substrate, and highly coaxial with its axis of rotation. Also, the gear of the driving flange is required to have sufficient fatigue resistance, wear resistance and mechanical strength.
On account of their excellent machinability, excellent surface properties, low cost and light weight, aluminum alloys have been widely used as the material of the cylindrical tubular substrate. However, to meet the dimensional and surface-roughness specifications, it is necessary to machine the peripheral surface of each cylindrical aluminum alloy substrate with high precision. It is necessary also to insert a flange for rotating the substrate with high precision in the layer-by-layer formation of a photoconductor. It is necessary further to clean contaminants from the outer substrate surface before forming the photoconductive layer. Since an aluminum alloy surface may undergo change depending on the storage environment, it is also necessary to take countermeasures, e.g., by covering the substrate surface with an oxide film. As a result, conventional aluminum alloy substrates have been made using many manufacturing steps at high cost.
Japanese Patent Document No. H02-17026 discloses a cylindrical tubular substrate that is lighter in weight, highly resistant chemically and thermally, neither oxidized nor deformed in air, and compatible with photoconductors. This substrate can be made by injection molding of a polyphenylene sulfide resin (hereinafter referred to as "PPS resin") to which carbon black is added for electric conductivity.
For such a cylindrical tubular substrate made of a conductive resin, a resin driving flange is preferred. The resin flange may be installed on the resin substrate by pressing the flange into an adhesive-coated insertion portion of the resin substrate. But it is difficult to fix the driving flange at an end of a cylindrical tubular substrate coaxially with the rotation axis of the substrate.
As described above, it is necessary to ground the cylindrical tubular substrate so that the substrate may function as one of the electrodes of the photoconductor. Typically, the cylindrical tubular substrate is grounded by installing a metallic spring at the time the resin driving flange is inserted and fixed to the substrate, so that the substrate and the shaft are electrically interconnected. This requires additional processing steps. Also, the cost of the photoconductor is increased, as conductive adhesive should be applied between the resin substrate and the non-conductive driving flange because of high contact resistance between the substrate and the flange.